1. Field of the Invention
The invention relates to tools and in particular to parallel action pivot handled tools. More specifically, the invention relates to cutting tools employing male and female dies, especially to hand operated cutting tools adapted to trim sheet materials such as venetian blind slats.
2. Description of the Prior Art
Parallel action pivoted hand tools are well known in the art in the form of parallel jaw pliers, which are widely available. U.S. Pat. Nos. 168,924 and 188,262 to Russell disclose the relevant structure in substantially the same form in which it is currently practiced.
Venetian blind trimmers are a commonly used installer's tool, used to adapt a premanufactured blind to the specific requirements of an opening. Often each slat of a blind must be trimmed at one end. For this purpose, male and female dies are attached to the jaws of a scissors action hand tool similar to a tin snip, and a depth guage is connected to one of the dies to provide a uniform depth-of-cut measurement for evenly modifying the length of any number of slats. The typical scissors action venetian blind trimmer brings the male and female dies together with a variable shear so that a slat is trimmed progressively from one edge to the other as the pivoted handles are closed. An ordinary shear cannot be used for this trimming operation because the end edge of a venetian blind slat is smoothly curved at each corner for transition to the forward and rearward edges of the slat, and this curve must be preserved for cosmetic uniformity among slats of a single blind.
The seemingly straight-forward task of trimming venetian blind slats with acceptable cosmetic uniformity presents several problems. First, the slats are slightly bowed from front to rear and tend to flatten under the pressure of a cutting tool, presenting an alignment problem between the edges of the slats and the corner curves on the cutting dies. Second, the slats are constructed from thin sheet material such as aluminum, and hence the edges are easily subject to burring if the clearance between male and female dies is excessive. The latter presents a recurrent problem with scissors-action trimmers since alignment between the dies is controlled only at the single pivot point between the shear handles. If either burring or uneven corner curves should result from a trimming operation, it is necessary to retrim, potentially producing unevenness among slat lengths, or to replace the ill-trimmed slat. For this reason it is highly desirable that a trimmer be accurate and consistent in its operation.
The present invention provides a solution to the problems of scissors-action venetian blind trimmers and correspondingly offers an improvement in parallel action jaw tools, especially those employing cooperating cutting edges.